Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $87.80   8.460%   $95.2279   $95.23   $95.25   $95.20  
  Purchase #2 $68.42   10.393%   $75.5309   $75.53   $75.55   $75.50  
  Purchase #3 $78.41   13.838%   $89.2604   $89.26   $89.25   $89.30  
  Purchase #4 $158.29   3.362%   $163.6117   $163.61   $163.60   $163.60  
  Purchase #5 $201.90   12.166%   $226.4632   $226.46   $226.45   $226.50  
  Purchase #6 $125.81   6.104%   $133.4894   $133.49   $133.50   $133.50  
  Purchase #7 $160.45   6.670%   $171.152   $171.15   $171.15   $171.20  
  7 purchase totals = $881.08       $954.7355   $954.73   $954.75   $954.80